n = int(input())
c = input()

a = c.count("R")
b = c[:a].count("W")
print(b)
 n = int(input()) n int(input()) int input() input c = input() c input() input a = c.count("R") a c.count("R") c.count c count "R" b = c[:a].count("W") b c[:a].count("W") [:a].count [:a] c :a a count "W" print(b) print b c = input() input() c a = c.count("R") c.count("R") a b = c[:a].count("W") c[:a].count("W") b n = int(input()) int(input()) n
n = int(input())
c = input()

a = c.count("R")
b = c[:a].count("W")
print(b)

